Maneuvering tow target



Dec. 10, 1968 w. c, WOODWARD MANEUVERING TOW TARGET Filed Sept. 25, 1966 INVENTOR WILMER C. WOODWARD A TORNEY United States Patent O 3,415,520 i MANEUVERING TOW TARGET Wilmer C. Woodward, Blue Bell, Pa., assignor to the United States of America as represented by the Secretary ofthe Navy Filed Sept. 26, 1966, Ser. No. 582,477 13 Claims. (Cl. 273-105.3)

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royal-ties thereon or therefor.

The present invention relates generally to tow targets I and more particularly relates to a ce-nter of gravity towed target capable of ying along an odset flight path that is selectively variable from that of the towing vehicle.

In order to evaluate and determine missile weapon system effectiveness against multiple targets, i-t is desirable that a maneuverable tow tar-get having the capability of -being able to y in formation be provided. Tow targets such as those disclosed in the copending application Ser. No. 429,176 for Off-set Tow Target by Wilmer C. Woodward et al. filed Jan. 29, 1965, have been invented which are capable of flying in flight paths parallel to and l.laterally separated predetermined dis-tances from a towing aircraft. Such targets when launched at a given -airspeed and altitude automatically assume the aforesaid separation distances and have no maneuvering capability. Frequently, during missile weapon system effectiveness tests, it is desirable both to vary the distance of lateral or vertical separation in flight and also to cause target movement from one side of the towing aircraft to :the other.

The general purpose of this invention is to provide a maneuverable tow target. Briefly, this is accomplished by equipping the `tow target with remotely actuatable apparatus for selectively adjusting the angle of incidence of movable foils and also for simultaneously maintaining the target in -a relatively constant roll attitude relative to the ground.

It is therefore an object of the present invention to provide a maneuverable tow target which by remote control is able to be positioned at selectively variable distances of separation from the towing vehicle.

Another object of -this invention is to provide a tow target capable of assuming a greater degree of lateral separ-ation from the towing vehicle with greater precision than is possible for heretofore known offset'tow targets.

A further object of this invention is to provide a tow target of inexpensive construction which is capable of being selectively maneuvered from one side of a towing aircraft to the other.

Other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the annexed drawing which illustrates preferred embodiments and wherein:

FIG. 1 represents a longitudinal view, partially in sec tion, of one embodiment of a tow'target according to the invention;

FIG. 2 represents a cross section of the target of FIG. 1 taken substantially along line 2 2;

FIG. 3 represents a view of the target from the top of FIG. 1 but reduced in size;

FIG. 4 represents a longitudinal view, partially in section, of another embodiment of a tow target according tothe invention; and

FIG. 5 represents a cross section of the target of FIG. 4 taken substantially along line 5--5.

Referring now to the embodiment of FIGS. 1 and 2, the tow target generally designated at includes a thin-walled, cylindrical body portion 12 which may be 3,415,520 Patented Dec. 10, 1968 made from plastic, cardboard, or other inexpensive lightweight material. The leading and trailing ends of the body portion 12 include pairs 14 and 15 of diametrically opposed apertures through which extend respectively parallel, vertical shafts 16 and 17, each being rotatable. Two vertical steering canards 18 are fixed to either protruding end of the shaft 16 while two vertical fins 19 are fixed to either protruding end of shaft 17. The trailing end .of the body portion further includes two horizontal fins 20 opposedly fixed thereto. Only the aft portion of one lin 20 is visible.

An internally mounted bulkhead 22 is spaced forwardly of the center of gravity CG of the target and provides Isupport for a pair of guide rollers 24 and a circular drive sheave 26 each mounted within the body portion 12 for rotation about axes parallel to the longitudinal axis of the target. The sides of the `body portion 12 include symmetrically positioned apertures 28 extending therethrough, each of the rollers 24 being positioned adjacent the interior side of a corresponding aperture 28. An endless belt 30 is arranged roughly in the shape of a figure 8 and has the lower loop extending about and in drivable engagement with the drive -sheave 26 and has the upper loop extending adjacent the rollers 24, through vthe apertures 28 and externally about the upper periphery of the body portion 12. The upper periphery of the body portion 12 includes protruding therefrom low friction strips 32 arranged to space the ybelt 30 from the outer periphery of the vbody portion 12. A swivel 34 is fixed to a point on the portion of the belt 30 which is arranged externally of the body portion 12 and forms a connecting member -between the trailing end of a tow line T extending from a towing aircraft (not shown) and the belt 30. As the drive sheave 26 is rotated, the belt 30 and, consequently, the swivel 34 and tow line T connected thereto are caused to move relatively about the upper periphery of the body portion 12.

Gear trains 40 and 42 respectively drivingly link the drive sheave 26 with the vertical shafts 1'6 and 17. A conventional servo motor 44 is carried within the body portion 12 and is arranged to drive the gear train 42 in response to actuation by a conventional receiver 45 including a power supply and being capable of responding to remotely transmitted instructions. The gear trains 40 and 42 are conventionally constructed so that the shafts 16 and 17 will be caused to rotate in the same direction through angles a and respectively and so that the swivel 34 will be peripherally moved to one side away from a vertical reference plane extending along the longitudinal axis A of the body portion 12 when the canards 18 and fins 19 are being positioned to have respective angles of incidence measured to the other side. Theangle a is greater than the angle as shown in FIG. 3 partly because the fins 19 are larger than the canards 18 and also so that when equilibrium is reaching the target will be more nearly aligned along its line of flight.

As shown in FIG. l, the axial spacing between the CG and the substantially normal plane including the swivel 34 and defined by the upper loop of lthe belt 30 is arranged so that a line extending -along the target-connected end of the tow cable T extends towards the vicinity of the CG with a sufficient degree of closeness as to maintain aerodynamic stability throughout the permissible excursion of the target as hereinafter described.

It is preferred in the embodiment described that the t-arget CG lie substantially along the longitudinal axis A of the target for greater ease in maintaining or achieving a selected roll attitude of the body portion 12. Ballast 46 and 48 are preferably aixed to the inner periphery of the :body portion 12 in order to counterbalance both the effect of securement of the servo motor 44 and receiver 45 to -the body portion and the effect attributable to the displacement of the gear trains 40, 42 and the drive sheave 26 from the longitudinal axis A of the target 10.

Referring now to FIG. 3, wthen the servo motor 44 drives the gear trains 42 and 40 and thereby causes the shaft 16 to rotate through an angle a from the longitudinal axis A to change the angle of incidence of the canards 18, the leading end of the target in flight is moved outwardly 'by the air stream thereby increasing the angle of incidence of the vertical fins 19 to the air stream. This generates a horizontal aerodynamic force component substantially normal to the axis of the target 10 and causes the target to move laterally away from the towing aircraft. If the swivel 34, and thereby the point of connection for the tow line T to the target 10, were fixed relative to the body portion 12, the target 10 would tend to be rotated about its longitudinal axis A until the resultant of the aerodynamic forces and the weight of the target lies along a line extending lfrom the target-connected end of the tow cable T. In consequence, the horizontal component of the side force generated on the fins 19 is reduced, and further lateral separation of the target 10 from the towing aircraft is limited. By controlling thel amount of rotation of the drive sheave 26, the point of connection of the tow cable T to the target may be caused to move about the periphery and away from the vertical reference plane as shown in dotted lines in FIG. 2 until the canards 18 and the fins 19 become substantially vertically oriented relative to ground. Since this tends to increase the horizontal side force, the target 10 further moves outwardly to a new equilibrium point; and a greater lateral separation of the target 10 from the towing aircraft is achieved yfor a given angle of incidence of the canards 18.

The angular deviation of the tow cable T from vertical changes as some function of the angle of incidence of the target 10 and its fins 19 which in turn is primarily affected by the angle of incidence of the canards 18. While this function is not a linear function, it has been found that a linear variation substantially approximates the function. Consequently, if the ratio of the maximum rotational excursion of the shaft 60 to the rotation of the drive shea-ve 26 and thereby the maximum peripheral excursion of the swivel 34 is carefully selected to maintain aerodynamic stability and a substantially vertical roll attitude relative to ground, 4both the drive sheave 26 and the shaft 16 maybe driven by the same motor. Satisfactory gearing ratios may be ascertained by calculating the angle of incidence of the canards 18 and the corresponding angular deviation of the tow cable T from vertical when the target 10 is positioned during flight at the maximum desired lateral separation, the fins 19 and the canards 18 being maintained in a substantial vertical orientation with respect to ground. Of course, the gearing ratio for the drive sheave 26 is affected by the relative diameters of the loops of the belt 30.

For a 40-pound target having a diameter of 7.5 inches, a length of approximately `6.3 feet, having vertical Iand horizontal fins each with exposed area of about 1.6 square feet and having vertical canards each with an exposed area of about 0.4 square feet, it has been found that a suitable gearing ratio for the angular excursion of the `tow cable T from one side through vertical to the other side relative to the range of angles of incidence of the canard is 136:7. For a target of the above configuration, it has been found that the vertical fins may be fixed in position as are the horizontal tins. For heavier targets, it has been found that greater side forces may be generated if the vertical fins are enabled to have a selectively adjustable angle of incidence as indicated above. For example, for a l21/2-inch diameter, 60-pound target having a length of about 61/2 feet, having horizontal and vertical fins each with exposed areas of 2.54 square feet, and

having canards having exposed areas of .475 square feet, a suitable Iratio for the angular excursion of the tow cable from one side through vertical to the other side relative to the range of angles of incidence of the canards and relative to the range of angles of incidence of the fins approximates :l2:4.

Referring now to another embodiment in FIGS. 4 and 5, a target 10' having the vertical canards 18 and vertical and horizontal fins 19' and 20' includes different structure for varying the angular deviation of the tow cable T from the vertical reference plane which replaces the bulkhead 22, guide rollers 24, drive sheave 26 and belt 30 of target 10. Target 10 instead includes a pair of bulkheads 50 and 52 spaced respectively forwardly and rearwardly of the center of gravity of the target. A cylindrical drum section 54 is mounted for rotation with shafts 56 and 58 extending respectively from the gear trains 42 and 40' along the longitudinal axis of the target 10. The drum section 54 includes a longitudinally oriented slot 60 and is of a size to fit closely in sliding engagement with the body portion 12 which in turn has an aperture 62 which is of a size sufficient to register with the slot 60 throughout the excursion thereof between positions of maximum displacement to either side of the vertical reference plane of the target las the drum section 54 is rotated. The inwardly extending end of shaft 56 terminates at the center of gravity of the target 10 in an eyelet 64 to which is connected the extended end of the tow cable T which passes through the aperture y62 and the slot 60. The gear trains 40 and 42 are so arranged that when the canards 18' and fins 19 are rotated to have respective angles of incidence measured to one Side, the drum 54 is rotated in a direction such that the corresponding angle of deviation of the tow cable from vertical is measured to the other side.

It is apparent lfrom the above that when the drum 54 is relatively 4rotated to a new position, the 4body portion 12 will undergo a corresponding axial rotation because of the engagement of the boundaries of the slot 60 with the tow cable T' until the resultant of the aerodynamic drag forces generated and the weight of the target lies in substantially the plane defined by the slot `60 and the longitudinal axis of the target. Consequently, by controlling the degree of rotation of the drum 54, the vertical ns 19' and the canards 18 may be maintained in a substantially vertical orientation relative to ground. Of course, it is preferred that the aperture `62 in the body portion 12' and the drum 54 be so designed as to reduce air turbulence to a minimum.

From the above it is now apparent that there has been provided a tow target which is capable of being positioned at selected separation distances from the towing aircraft and is capable of being maneuvered to either side of the towing aircraft.

As indicated by the above-described embodiments, the target includes movable canards and fixed or movable fins. It is contemplated, however, that under some conditions of target configuration, the canards may be eliminated, without departing from the invention herein disclosed and claimed, if movable fins are included which fins are appropriately configured and positioned for aerodynamic stability. The various combinations of movable foils make possible a variety of differently sized and configured targets.

While the above-described embodiments have been described in terms of variable lateral separation from the towing aircraft, it is contemplated that variable vertical separation can be similarly achieved by maintaining the steering canard shaft 16 in a horizontal orientation instead of the vertical orientation described. The use of the terms vertical, horizontal and lateral is not intended to limit the described embodiments to a particular orientation.

It should be understood, of course, that the foregoing disclosure relates only to preferred embodiments of the invention and that numerous modifications or alterations may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A maneuverable tow target comprising:

an elongated body portion;

foil means movably mounted on said body portion;

orientation means carried by said body portion intermediate the ends thereof and including means for contacting the trailing end portion of a tow cable for varying the peripheral position thereof; and u control means operatively connected to said foil means and said orientation means for correspondingly and selectively varying the angle of incidence of said foil means, together with the peripheral position of the cable about the longitudinal axis of said body portion to maintain a selected roll attitude of said body portion while said target is in flight.

2. A target according to claim 1 wherein said foil means includes:

rin means rotatably mounted on the trailing end of said body portion, said iin means being operatively connected with said control means.

3. A target according to claim 1 wherein said foil means includes:

contacting further includes:

means engageable with said end portion of said cable for selectively rotating said end portion about the longitudinal axis of said body portion.

6. A target according to claim 5 wherein:

said body portion is hollow and has a pair of peripherally spaced apertures each providing communication with the interior of said body portion; and

said orientation means further includes selectively rotatable belt driving means positioned within the interior of said body portion and operatively connected to said control means, endless belt means arranged in driveable engagement with said driving means and extending through said apertures in said body portion to form a loop carried externally of said body portion, said loop being selectively movable in response to rotation of said driving means, and said cable engaging means thereof includes means connected to said loop and adapted for having connected thereto said end portion of said cable.

7. A target according to claim 6 wherein:

said foil means includes means canard rotatably mounted on the leading end of said body portion; and

said control means further includes rst means operatively connected to said canard means for varying the angle of incidence thereof and second means drivingly connected to said belt driving means for rotating same 6 as a function of the angle of incidence of said canard means. 8. A target according to claim 7 wherein said control means further includes:

remotely actuatable servo motor means drivingly connected to said first and second means.

9. A target according to claim 8 wherein:

said foil means further includes a pair of oppositely extending, rotatably mounted ins; and

said control means further includes means operatively connected to said ns for selectively varying the angle of incidence thereof.

10. A target according to claim 5 wherein:

said orientation means further includes cable connecting means positioned at the center of gravity of said target and adapted for having connected thereto said end portion of said tow cable;

said body portion includes an opening positioned adjacent said center of gravity; and

said cable engageable means further includes a surface rotatably mounted within said body portion and positioned adjacent said opening and said connecting means and having a slot for receiving therethrough said end portion of said tow cable for connection to said connecting means;

said opening of said body portion being of a size to register with said slot during selected rotation of said surface.

11. A target according to claim 1t] wherein:

said foil means includes canard. means rotatably mounted on the leading end of said body portion; and

said control means further includes first means operatively connected to said canard means for varying the angle of incidence and second means drivingly connected to said surface for rotating same as a function of the angle of incidence of said canard means.

12. A target according to claim 11 wherein said control means further includes:

remotely actuatable servo motor means drivingly c011- nected to said rst and second means.

13. A target according to claim 12 wherein;

said foil means further includes a pair of oppositely extending, rotatably mounted tins; and

said control means further includes means operatively connected to said tins for selectively varying the angle of incidence thereof.

References Cited UNITED STATES PATENTS 2,432,548 12/ 1947 Taylor 244-3 3,311,376 3/1967 Woodward et al. 273-1053 FOREIGN PATENTS 737,318 9/ 1955 Great Britain. 778,185 7/ 1957 Great Britain.

OTHER REFERENCES Aviation Week, June 30, 19.52, p. 36.

ANTON O. OECHSLE, Primary Examiner.

M. R. PAGE, Assistant Examiner.

U.S. Cl. X.R. 

1. A MANEUVERABLE TOW TARGET COMPRISING: AN ELONGATED BODY PORTION; FOIL MEANS MOUNTED ON SAID BODY PORTION; ORIENTATION MEANS CARRIED BY SAID BODY PORTION INTERMEDIATE THE ENDS THEREOF AND INCLUDING MEANS FOR CONTACTING THE TRAILING END PORTION OF A TOW CABLE FOR VARYING THE PERIPHERAL POSITION THEREOF; AND CONTROL MEANS OPERATIVELY CONNECTED TO SAID FOIL MEANS AND SAID ORIENTATION MEANS FOR CORRESPONDINGLY AND SELECTIVELY VARYING THE ANGLE OF INCIDENCE OF SAID FOIL MEANS, TOGETHER WITH THE PERIPHERAL POSITION OF THE CABLE ABOUT THE LONGITUDINAL AXIS OF SAID BODY PORTION TO MAINTAIN A SELECTED ROLL ATTITUDE OF SAID PORTION WHILE SAID TARGET IS IN FLIGHT. 